Development of vegetation in a constructed wetland receiving irrigation return flows

The Fairview Constructed Wetland, a complex of replicated wet meadow (primary filter) and shallow marsh (shallow wetland) cells, was built in southeast Idaho in 1999 and planted with seven native plant species. The development of aboveground biomass and root mass and the accumulation of litter for each cell and for each species are described here. Establishment patterns varied among species and wetlands. Juncus balticus and Carex nebrascensis contributed disproportionately to the biomass in the primary filter cells. In these wetlands, aboveground biomass increased from an overall average of 443 in 2000 to 560 g/m2 in 2003, while root mass increased from 387 to 1108 g/m2. Litter mass increased from 230 in 2001 to 829 g/m2 in 2003. In the shallow wetlands, average aboveground biomass increased from 82 in 2000 to 391 g/m2 in 2003, while root mass increased from 108 to 574 g/m2 over this same period. From 2001 to 2003, litter mass increased from 68 to 214 g/m2. All measures of biomass and litter in the shallow wetlands were less than the corresponding values in the primary filter cells over the same time period. Still, biomass measures differed among shallow wetlands and some of this variation was explained by the differences in each wetland's hydrograph.